How Do I Enter NULL In A Table Cell In The Enterprise Manager UI For Table Data Entry?

I have a column defined as smalldatetime. Default length (4), and "allow NULLS" is checked.In the Enterprise Manager UI, when i enter data into that table row, if i just tab past that column, all is well, and the value is represented in the UI as <NULL>.The problem comes once i ever enter a date into that column.  Say i have entered a date (all is well), and now i want to remove that entry and go back to NULL (after the date value has been committed, different entry session, say).How is that done?It seems to me, once a date has ever been entered into that column, now, if i try to remove it, i get the error "The value you entered is not consistant with the data type or length of the column, or over grid buffer limit".  I have tried deleting the value, entering spaces, entering the string NULL or the string <NULL>; maybe some other tries as well, but none works, i always get that error message and am not allowed to proceed past that cell until i restore a date value to it.  I want to get back to <NULL>.Anybody know?Thank you.Tom